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    A novel wearable assistive device for jaw motion disability rehabilitation : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Auckland, New Zealand
    (Massey University, 2014) Wang, Xiaoyun
    Temporomandibular disorder (TMD) is a group of dysfunctions in the masticatory system that cause muscle stiffness and weakened masticatory ability. TMD is commonly suffered by a considerate percentage of the population, impairs oral hygiene and brings inconveniences to a great number of patients. The therapeutic exercise with significant efficacy is widely advised among patients in the treatment of the mandibular hypomobility to reduce pain and increase the inter-incisal opening of the mouth. This thesis proposes a novel wearable device to passively assist to deliver the mandibular movement. The mandible, attached to the skull via masticatory muscles and pivoted at the condyles at the temporomandibular joint (TMJ), can be simplified as moving in the two-dimensional sagittal plane. A planar four-bar linkage was synthesized to reproduce the specified normal jaw motion in terms of incisor and condyle trajectory on the coupler point to meet the kinematic specification. Adjustable lengths of the links were used to achieve a group of trajectories of any possibility. The prototype of the linkage has been fabricated, integrated with the sensory units and electronic hardware into a Mechatronic system. The dynamics of the entire system was analyzed, along with the model thoroughly built up in Simulink, to facilitate further controller design. A closed-loop control scheme based on the device was proposed, and it is able to achieve the accurate position control to the crank to ensure the position of the jaw to be notified. A series of experiments with the device has been carried to evaluate the performance of the controller, with the control algorithm implemented into a micro-controller based board. The exoskeleton was then evaluated in terms of the kinematic and dynamic interaction in the hybrid human-machine system, in which the condyle movement was recorded by AG500 tracking machine. Simulation and experimental methods were respectively developed to investigate the joint force which is in-vivo inaccessible. Simulation was conducted by adding the dynamic model of the mandible into the linkage model with controller. A test-rig was designed to mount the skull and the jaw replicas which simulated the counterparts in human body. Experiments were carried to evaluate the joint force and the performance of the controller; results obtained from both simulations and experiments have indicated the force level inside the TMJ is rather small compared with the one in the circumstance where maximum chewing force is applied.
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    A novel, neuroscience-based control paradigm for wearable assistive devices : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Albany, New Zealand
    (Massey University, 2013) Noble, Frazer Kingsley
    The biological domain has evolved in such a way that it effciently overcomes many problems we struggle to solve in the engineering domain; for example, bipedal locomotion, which requires a number of desirable attributes, e.g. compliance and adaptability. As such, the aim of this research has been to provide a bridge between the biological and engineering domains, capturing these attributes, and developing an enabling control technology. The application of this research has been around wearable assistive devices: devices that assist rehabilitation and recuperation of lost or impaired functions or enable an end user to perform difficult to complete tasks. As such, this thesis presents a novel, neuroscience-based control technology for wearable assistive devices. Major contributions of this work include reproducing both biological movement's compliant and adaptive properties in the engineering domain. The presented approach consists of using an assistive device, whose joints are antagonistically actuated using compliant pneumatic muscles, and central pattern generators. The assistive device's actuators make the arm robust to collision and give it smooth, compliant motion. The pattern generators produce the rhythmic commands of the joints of the assistive device, and the feedback of the joints' motion is used to modify each pattern generator's behaviour. The pattern generator enables the resonant properties of the assistive device to be exploited to perform a number of simulated rhythmic tasks. As well as providing a wealth of simulated and real data to support this approach, this thesis implements integrate-and-fire, Izhikevich, and Hodgkin-Huxley neuron models, comparing their output based on ring patterns observed in neurons of the nervous system. These observations can be used as a mechanism for deciding the "realism" needed to represent a neural system's characteristics. In addition, Hill's muscle model has been presented, and simulation of an implemented soleus muscle carried out. Parametric variation provides quantitative insight into passive and active series and parallel elements' roles in generating tension and tension's timeresponse characteristics. Furthermore, an antagonistically coupled pair of extensor and flexor muscles have been presented and shown to effect compliant joint actuation of a modelled limb under differential activation. Co-activation of the extensor and flexor has been shown to increase a joint's stiffness, leading to increased stability and rejection of limb perturbation.